Dear CarmenLove, I'm not sure how this works either, and I'm certainly not a lawyer. However upon some reading it seems that you could file on the ground of unreasonable behaviours (including physical/verbal abuse and drug taking...)
You might want to check your work benefits to see if they offer assistance with legal issues. Look up local organizations who provide help to emotionally/physically abused people (most of us who live with substance abusers at least fall into the emotionally abused category.) They should at least be able to give you some guidance on where to look for more information if not actual legal help with the case. In rare occasions you might be able to get a lawyer to take your case pro bono.
In the mean time, just gather any pieces of evidence you have, document everything you know about his behaviours - the more detailed the better. Whether you file for the divorce on your own or get some legal help elsewhere, the more information you can provide, the more it's going to help your case.
Good luck and big hugs to you.